Looking at the AAC mk13. Just built my first ar in .300 blackout and now I am addicted. Last to buy is the barrel and I'm looking at the noveske 14.5 or 16" barrel with a 90t, can I pin that or is that a pain in the ars? Is there another hight end can I should be looking at to buy? I started looking at the silencershop.com today called and I've got the fever,,,, tax season coming up!!!!